Oxidized polymers have found a number of applications, one of which is as an intermediate for lubricating oil additives.
Lubricant deterioration in high speed engines causes the formation of lacquer, sludge and carbon deposits on the interior surfaces of the engines which accelerates wear and reduces engine efficiency. To reduce the tendency for such deleterious products to deposit on the surfaces of the engine it is known to incorporate in the lubricating oil additives having dispersancy and/or detergency properties.
The continuing search for and the necessity of having available ashless dispersants and/or detergents additives for motor oils is well known. Since the development of the positive crankcase ventilation system (PCV) there is a greater demand than ever for improved additives of such types.
It is also well known that lubricating oils have a tendency to become thin at elevated temperatures while becoming thick at low temperatures, and thus it is generally necessary to add additives to such lubricants which improve their viscosity-temperature relationships. For example, in the case of a crankcase lubricating oil in a cold engine, it is desirable that the oil not become so thick that it is difficult to start the engine; while, when the engine is hot it is necessary that the oil remains sufficiently viscous that an oil film is maintained between the moving parts.
Various products have been developed for the purpose of providing the dispersant and/or detergent function.
Culbertson, et. al., U.S. Pat. No. 3,544,520 issued Dec. 1, 1970, discloses and claims as ashless dispersants the products prepared by subjecting an olefin polymer having a molecular weight of about 200-2,000; such as a polybutene or polypropylene to oxidation in the presence of a catalyst such as manganous carbonate, and the oxidized polymer then condensed with formaldehyde and a polyalkylene polyamine. Such condensation products while effective as ashless dispersants, do not impart V. I. improving properties to lubricating oils.
Additives, imparting sludge inhibiting and detergent properties to lubricating oils, prepared by reacting oxidized degraded interpolymers of propylene and ethylene having a molecular weight of at least about 1,000, with maleic anhydride, and neutralizing the acidic intermediate with an alkylene polyamine, is described in U.S. Pat. No. 3,316,177.
Culbertson, et. al., U.S. Pat. No. 3,872,019 issued Mar. 18, 1975 discloses and claims bi-functional lubricant additives exhibiting dispersant and V.I. improving properties obtained by the Mannich Condensation of an oxidized long-chain high molecular weight amorphous copolymer of essentially ethylene and propylene having a number average molecular weight of at least about 10,000 and at least 140 pendant methyl groups per 1,000 chain carbon atoms, with a formaldehyde yielding reactant and a primary or secondary amine or polyamine, said reactants being employed in the molar ratio of from about 1:2:2 to about 1:20:20, respectively.
Others have also made lubricating oil additives by oxidizing various copolymers.
It has been noted that during the oxidation of the copolymer, the product sometimes becomes undesirably dark colored. Dark colored oxidized intermediates generally lead to dark colored derivatives. Also, reaction time for the oxidation is relatively long and reactor throughput is less than desired. In some cases it is desirable to produce a product having lighter color. In many cases, it is desirable to increase the rate of oxidation so as to increase reactor throughput, even without maintaining product color. It is an object of this invention to provide a process for oxidizing copolymers while controlling reaction rate and/or product color.